Claims
- 1. A method of detecting a latent photocopier tracking signature printed on a document produced by a color photocopier, comprising:
generating a plurality of color separations that digitally represent the document wherein each of the plurality of color separations are defined by a plurality of pixel values; generating an output image based on differences between corresponding pixel values of at least two of the plurality of color separations; and displaying the output image to view the photocopier tracking signature.
- 2. The method of claim 1, further including:
before the displaying step, enhancing the contrast of the output image.
- 3. The method of claim 2, wherein the enhancing step includes:
performing a histogram stretching technique on the output image.
- 4. The method of claim 2, wherein the enhancing step includes:
performing a histogram equalization technique on the output image.
- 5. The method of claim 1, wherein the first generating steps includes:
scanning the input document into a digital image processing system; and storing the resulting plurality of color separations as separate bitmapped gray scale images.
- 6. The method of claim 1, wherein the first generating step includes:
generating a red color separation, a blue color separation, and a green color separation; and storing the red, green, and blue separations as separate bitmapped gray scale images.
- 7. The method of claim 1, wherein the second generating step includes:
generating an output image for each of a plurality of different combinations of the color separations.
- 8. The method of claim 1, wherein the displaying step includes:
displaying the output image on a display monitor.
- 9. The method of claim 1, wherein the displaying step includes:
printing the output image on a printer.
- 10. The method of claim 1, wherein the latent photocopier tracking signature is yellow, and the second generating step includes:
generating the output image based on differences between corresponding pixel values of a blue color separation and a green color separation.
- 11. An image processing system comprising:
an input terminal that supplies digital image data representing an input document produced by a color photocopier, the digital image data including a plurality of pixel values grouped together to form a plurality of color separations that represent the input document, and the input document having a latent photocopier tracking signature printed thereon; an image processing unit that generates an output image based on the digital image data, the image processing unit generating the output image based on differences between corresponding pixel values of at least two of the plurality of color separations; and an output terminal for displaying the output image to view the photocopier tracking signature.
- 12. The system of claim 11, wherein a contrast of the output image is enhanced before the output image is displayed.
- 13. The system of claim 12, wherein a histogram stretching technique is used to enhance the output image.
- 14. The system of claim 12, wherein a histogram equalization technique is used to enhance the output image.
- 15. The system of claim 11, wherein the input terminal includes a scanner that scans the input document into the system, and the plurality of color separations are stored as separate bitmapped gray scale images.
- 16. The system of claim 11, wherein the plurality of color separations include a red color separation, a blue color separation, and a green color separation, and the red, green, and blue color separations are stored as separate bitmapped gray scale images.
- 17. The system of claim 11, wherein the image processing unit generates an output image for each of a plurality of different combinations of the plurality of color separations.
- 18. The system of claim 11, wherein the output terminal includes a display monitor that displays the output image.
- 19. The system of claim 11, wherein the output terminal includes a printer that prints the output image.
- 20. The system of claim 11, wherein the latent photocopier tracking signature is yellow, and the output image is generated based on differences between corresponding pixel values of a blue color separation and a green color separation.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of application Ser. No. 09/216,236 filed Dec. 18, 1998.
Continuations (1)
|
Number |
Date |
Country |
Parent |
09216236 |
Dec 1998 |
US |
Child |
10280311 |
Oct 2002 |
US |